Lombardy is a region in northern Italy bordering Switzerland. It is physically divided into three regions. In the north is an Alpine region of peaks and glaciers adjoined to the south by an area of upland pastures and lakes. To their south is the rich valley of the River Po which, with its many tributaries, drains the sub-Alpine area. The Lombard plain, located centrally, lies at the confluence of serveral Alpine passes and has been much sought after throughout history. The area has variously been part of the Roman Empire, an independent kingdom, under Charlemagne's rule, and later under that of Spain, Austria and France. Ruskin discusses the significance of its medieval history ( Works, 24.135) and its significance throughout Italian history ( Works, 19.443-44). It was incorporated into Italy in 1859. In Modern Painters Ruskin uses the landscapes of Lombardy and Lincolnshire in his argument for the importance of a sense of detail in the rendering of landscape.